1. Field of the Invention
This invention relates to a method for preparing perfluoroalkyl-substituted heterocyclic compounds. More particularly, the invention relates to a method for preparing such compounds by reacting a perfluoroalkyl bromide with heterocyclic substrates in the presence of a catalytic amount of iodine or an iodine generating compound.
2. Description of the Prior Art
Perfluoroalkyl-substituted heterocyclic compounds are used today as chemical intermediates for many chemicals which are utilized as pesticides, herbicides, fungicides, bactericides and as anti-inflammatory and analgesic agents. In particular, U.S. Pat. No. 3,609,158, issued to Torba on Sept. 28, 1971, describes pesticidal and herbicidal derivatives of trifluoromethylpyridine. Further, U.S. Pat. No. 3,787,420, No. 3,787,422, and No. 3,787,425, all issued on Jan. 22, 1974, describe derivatives of trifluoromethyl pyridines which are utilized as fungicides and bactericides. Japanese Kokai 74/35,386, published by Maeda et al. on Apr. 1, 1974, shows trifluoromethyl pyridine derivatives as anti-inflammatory and analgesic agents. Compounds made by the present process may be utilized in making these types of derivatives.
In the past, perfluoroalkyl-substituted heterocyclic compounds were made by reacting perfluoroalkyl iodides (not bromides) with the heterocyclic substrate in the presence of a free radical generating compound such as organic peroxides and aliphatic azo compounds. U.S. Pat. No. 3,271,441, issued to Brace on Sept. 6, 1966, discloses such a process.
While perfluoroalkyl iodides have been used to prepare perfluoroalkyl-substituted heterocyclic compounds, efforts to utilize less expensive perfluoroalkyl bromides have been unsuccessful. U.S. Pat. No. 3,890,326, issued to the present inventor on June 17, 1975, shows that an uncatalyzed vapor phase reaction of a heterocyclic compound and trifluoromethyl bromide results only in the bromine substitution of a hydrogen on the heterocyclic ring, thereby producing fluoroform (CF.sub.3 H) and a brominated heterocyclic product. Virtually, no perfluoromethyl-substituted heterocyclic products were made by this method.
Therefore, a need exists for a process for making perfluoroalkyl heterocyclic compounds which can utilize as a reactant perfluoroalkyl bromides instead of the more costly perfluoroalkyl iodides. It is believed that the present invention satisfies this need.